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Decorative flower or edible food production - how is the latent genetic machinery driven in plants?

Have you ever thought of what is the genetic mechanism that mediates and ultimately gives rise to the beautiful flowers that you buy as a gift for your loved ones? It would probably be very fascinating for you as well to get an insight into the molecular process of fruit/vegetable/grain production being consumed by us everyday, which commences through initiation of flowering in a particular plant. Let’s get some very basic knowledge on this biological phenomenon that we observe in nature and is directly related to our survival.

The onset of flowering is a key developmental transition in the plant life cycle and is regulated by different environmental factors such as photoperiod, temperature and endogenous cues like circadian clock, gibberellic acid and age of the plant. Arabidopsis thaliana/Thale cress has been extensively used as a model system by researchers for unveiling the molecular biology of flowering which encompasses several reasons: its small genome size, easy handling, short life cycle, comparatively fast generation time and prolific seed production.

A. thaliana is a facultative long day plant where flowering is regulated by a key mobile protein, FLOWERING LOCUS T (FT) that is known as florigen. FT expression is dependent on CONSTANS (CO) in leaves under long day (LD) where different other genes play positive and negative roles in regulating FT function. FT is transported from leaves to shoot apical meristem (SAM) where it interacts with a basic leucine zipper (bZIP) domain transcription factor, FD. In the SAM, the FT–FD complex induces expression of floral meristem identity genes such as LEAFY (LFY) and APETALA1 (AP1) via SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and this leads to commencement of flower formation. During winter, a MADS-box DNA binding protein FLOWERING LOCUS C (FLC) plays the central role in suppressing the expression of FT. Exposure to low temperatures (vernalization) induces expression of genes that repress FLC expression during warm temperature of the following spring, relieving the repression of FLC on FT and allowing the plant to initiate flowering process through FT action.

While flowering mechanisms are well understood in A. thaliana, they are less well perceived in other higher plant groups such as ornamental plants and crops. Therefore, scientists use knowledge gained from A. thaliana as a fundamental basis to investigate the genetic mechanism that regulates flowering time in higher plant species.